US Defence Secretary Leon Panetta has condemned the militants behind the Algerian hostage crisis and warned them: "Those who would wantonly attack our country and our people will have no place to hide."

In a speech in central London, Panetta vowed that the US government is "working around the clock to ensure the safe return of our citizens".

The former CIA chief said: "Even as we continue to try and gather better information about what is happening, let me make a few points.

"First, regardless of the motivation of the hostage takers, there is no justification, no justification, for the kidnapping and murder of innocent people, innocent people going about their daily lives.

"Second, we are working around the clock to ensure the safe return of our citizens and we will continue to be in close consultation with the Algerian government.

"And third, terrorists should be on notice that they will find no sanctuary, no refuge. Not in Algeria, not in North Africa, not anywhere.

"Those who would wantonly attack our country and our people will have no place to hide."